Have you ever been to Poughkeepsie?

Scene: a local plastic-ware shop. A man is trying to buy a plastic bread bin. After much fumbling with the cardboard box, the shopkeeper declares there is no price marked. An unseen voice from the back boldly states "$26.20" (£8.70).

"$26?" cries the customer in shock, "That's expensive isn't it?"
"Well, it's good plastic" (shades of Monty Python's "beautiful plumage" there)
"Yes, but $26? That's a lot of money"
"Well how much do you want to pay?" asks the shopkeeper, sensing the wild guess from the back might be off the market rate but there is a chance of a deal to be done.
"I don't know, it just seems pricey compared to a few years ago"
"Yeah, but a few years ago we didn't have the MRT!" [MRT=light rail network]

The resulting stunned silence reminds of a scene in the French Connection where Gene Hackman's detective character in mid flow of interrogating a known miscreant suddenly throws in "Have you ever been to Poughkeepsie?" The confused crim is thrown off his well-rehearsed alibi routine wondering what
possible crime in a small, up-state New York town he is now being linked with.

In both cases, a brilliant example of a dissonant response which leaves no room for logical reply.